44 lines
1.0 KiB
Rust
44 lines
1.0 KiB
Rust
fn fib(n: i64) -> Option<i64> {
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// A function declared inside another function does not pollute the outer namespace.
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fn actual_fib(n: i64) -> i64 {
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if n < 2 {
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n
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} else {
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actual_fib(n - 1) + actual_fib(n - 2)
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}
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}
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if n < 0 {
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None
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} else {
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Some(actual_fib(n))
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}
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}
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fn main() {
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println!("Fib(-1) = {:?}", fib(-1));
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println!("Fib(0) = {:?}", fib(0));
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println!("Fib(1) = {:?}", fib(1));
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println!("Fib(2) = {:?}", fib(2));
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println!("Fib(3) = {:?}", fib(3));
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println!("Fib(4) = {:?}", fib(4));
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println!("Fib(5) = {:?}", fib(5));
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println!("Fib(10) = {:?}", fib(10));
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}
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#[test]
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fn test_fib() {
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assert_eq!(fib(0).unwrap(), 0);
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assert_eq!(fib(1).unwrap(), 1);
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assert_eq!(fib(2).unwrap(), 1);
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assert_eq!(fib(3).unwrap(), 2);
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assert_eq!(fib(4).unwrap(), 3);
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assert_eq!(fib(5).unwrap(), 5);
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assert_eq!(fib(10).unwrap(), 55);
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}
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#[test]
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fn test_invalid_argument() {
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assert_eq!(fib(-1), None);
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}
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